chem 241 lec 1
What is a catalyst?
A species that increases reaction rate by providing a lower activation energy pathway and is regenerated (not consumed overall).
Why can small amounts of catalyst convert large amounts of reactant?
Because the catalyst is reused (high turnover), so one catalyst molecule can produce many product molecules.
Does a catalyst change equilibrium (Keq) or ΔG°?
No. It only helps the system reach equilibrium faster (speeds forward + reverse).
What is atom economy? Why is A + B → C typically good atom economy?
How well a reaction converts reactant atoms into the desired product (less waste = higher atom economy). Few/no byproducts → most atoms end up in the product.
Why are solvents important in green chemistry?
Solvents are often the largest source of waste, so reusing or avoiding solvents improves sustainability.
Why is catalysis essential for life?
Biological reactions are too slow under normal conditions; enzymes catalyze them so life can function at mild temperatures/pH.
Why do enzymes often use transition metals?
Transition metals can switch oxidation states, bind substrates strongly, and stabilize reactive intermediates → enabling fast/selective catalysis.
Is all life solar-powered?
Mostly yes indirectly, but some ecosystems (thermal vents) use chemosynthesis driven by inorganic chemical energy, not sunlight.
What does it mean that biomolecules exist as mirror images (chirality)? What is “homochirality” in life on Earth?
Many molecules have two enantiomers (mirror-image forms) that can behave differently biologically. Life uses mostly one enantiomer form (e.g., mostly L-amino acids), suggesting a common origin event.
Why do meteorites often contain a 50:50 mix of amino acid enantiomers?
Abiotic synthesis is usually non-selective, producing racemic mixtures without biological selection/catalysis.
What is steam methane reforming (SMR)?
Industrial process making H₂ from natural gas using steam + heat + catalyst.
What is the overall SMR reaction (with water-gas shift included)?
CH₄ + 2H₂O → CO₂ + 4H₂
Why is SMR widely used? What is a major use of H₂ produced by SMR?
It’s currently the most cost-effective large-scale method to produce hydrogen. Upgrading crude oil (hydrotreating/hydrocracking) to produce cleaner hydrocarbons.
Why does methane leakage matter so much?
CH₄ has strong greenhouse effect, so leaks can greatly increase the total emissions footprint.
What is the Haber–Bosch process used for?
Converting atmospheric N₂ into NH₃ (ammonia) for fertilizer production.
Write the balanced Haber–Bosch reaction.
N₂ + 3H₂ ⇌ 2NH₃
Why is Haber–Bosch considered one of the most important industrial processes ever?
It enabled large-scale fertilizer production, sustaining ~30–50% of the global population.
What does “We are made from air” mean in Haber–Bosch context?
Much of the nitrogen in human proteins originated as atmospheric N₂ fixed into fertilizer via H-B.
What is a common fertilizer produced from ammonia?
Ammonium sulfate, (NH₄)₂SO₄ (plus others like urea, ammonium nitrate).
Why does Haber–Bosch contribute to CO₂ emissions?
The required H₂ is commonly made by steam reforming methane, producing CO₂.
How is Haber–Bosch connected to WW1 Germany?
It reduced reliance on imported nitrates during the nitrate blockade by producing ammonia domestically.
What is grey hydrogen?
H₂ from methane steam reforming with CO₂ released to atmosphere.
What is blue hydrogen?
H₂ from methane steam reforming with CO₂ captured + geologically sequestered (CCS).
What is green hydrogen?
H₂ from electrolysis of water powered by low-carbon electricity.
Write the overall steam reforming + shift reaction.
CH₄ + 2H₂O → CO₂ + 4H₂
What is white hydrogen?
Naturally occurring underground H₂ formed by geologic redox processes (e.g., Fe oxidation + H⁺ reduction).
Why does the world want white H₂?
It could provide low-carbon H₂ without CO₂ emissions or large electricity input, reducing need for CCS/electrolysis infrastructure.
What does the IPCC conclude about recent global warming?
~1°C warming has been primarily caused by human-made greenhouse gas emissions, especially CO₂.
Why is CO₂ the main focus for emission reduction?
It’s a major greenhouse gas from energy + industry and it accumulates in the atmosphere.
What are “forever chemicals”?
PFAS compounds that are extremely stable and persist for decades in the environment.
Most “forever chemicals” are PFAS
Per- and polyfluoroalkyl substances.
Why are PFAS widely used in industry? Give 3 common uses of PFAS.
They have low friction, repel water/oil, and are heat/chemically stable. Fire-fighting foams, non-stick coatings, stain/water-resistant fabrics (also food packaging liners).
What does “per-” mean in PFOA (perfluorooctanoic acid)?
The carbon chain is fully fluorinated (all possible H replaced by F).
Why do PFAS last so long in nature? Why do PFAS repel water and stains?
The C–F bond is extremely strong, so PFAS resist degradation reactions. Fluorinated surfaces have very low surface energy and weak intermolecular attractions → liquids don’t wet the surface.
Why are PFAS environmentally concerning?
They persist, spread globally, and some are toxic at low concentrations and can accumulate.
What evidence shows electrons behave like particles?
The photoelectric effect (electrons ejected by light above a threshold energy).
What evidence shows electrons behave like waves?
Electron diffraction patterns from crystals.
What is de Broglie’s equation?
λ= h/ mv
What does de Broglie’s equation mean conceptually?
Particles (especially electrons) can have a measurable wavelength, enabling diffraction.
What does XPS measure?
The kinetic energy of photoelectrons ejected from a surface to determine binding energies (element + chemical state).
What is the key energy relationship in XPS/photoelectric effect?
Photon energy is converted into binding energy + kinetic energy (plus work function in XPS).
State Heisenberg’s Uncertainty Principle.
ΔxΔp≥ h/4 π
Why does uncertainty matter for atomic structure?
Electrons can’t have exact position + momentum → they must be described by probability/orbitals, not classical paths.
Why do we need Schrödinger’s equation?
Because electrons behave like waves, so atomic structure must be described using wave mechanics (not classical particle mechanics).
What is the wavefunction Ψ?
A mathematical function that describes the electron’s quantum state (wave behavior in an atom).
What does ∣Ψ∣ 2 represent?
The probability density of finding the electron at a given position.
What does solving Schrödinger’s equation give you?
The allowed wavefunctions (orbitals) and their corresponding energies.
Why do electrons have fixed/quantized energy levels?
Only certain standing wave solutions are allowed in atoms → discrete energies.
What is the standing wave analogy for orbitals?
Like a vibrating string: only wave patterns that “fit” are stable → allowed orbitals.
How does Schrödinger’s equation relate to spectroscopy/XPS?
It explains discrete orbital energies; electrons are ejected only if photon energy exceeds binding energy (measured in XPS).
Write the simplified Schrödinger equation.
ite the simplified Schrödinger equation.
^
HΨ=EΨ
What does the Hamiltonian operator
^
H represent?
The total energy operator
^
T
+
^
V
What does solving Schrödinger’s equation give you?
Allowed energies (E) and wavefunctions/orbitals (Ψ) → orbital shapes.
What does ∣Ψ∣ 2 represent physically?
Probability density of finding the electron at a position.
List key requirements for a physically valid wavefunction.
Single-valued, finite, continuous/smooth, and normalizable.
Why can Schrödinger’s equation be solved exactly for H but not He?
H has only one electron (2-body). He has electron–electron repulsion, making it a many-body problem.
How do we handle multi-electron atoms if exact solutions aren’t possible?
Use approximations (hydrogen-like orbitals + effective nuclear charge / average field).
Why do we use spherical coordinates (r, θ, φ) for the H atom?
Because hydrogen’s potential depends only on distance r, so the system is spherically symmetric.
How is the H-atom wavefunction written after separation of variables?
Ψ(r,θ,ϕ)=R(r)P(θ)F(ϕ)
What does the quantum number n represent, and what values can it take?
Principal energy level/size; n = 1,2,3…
What does ℓ represent and what values can it take?
Orbital angular momentum / orbital shape; ℓ = 0 to n−1
What does mℓ represent and what values can it take?
orbital orientation; mℓ= -ℓ, ..., + ℓ
What are the ℓ letter labels?
ℓ=0 s, ℓ=1 p, ℓ=2 d, ℓ=3 f.
What orbitals exist for n = 3?
3s, 3p, 3d.